Further history events to be finalized.
-arbitrary Cold War events
-1950s: additional oil fields are discovered on Ojin, Jimmu and Tenji.
-more arbitrary Cold War events until the fall of the U.R.S.S.
-arbitrary contemporary events

Final Total: 140.670T
New construction (15.330T) allowed by scrapping of existing warships starting in 1927.[/spoiler]

LNT (London Naval Treaty):
Firmataries:
United States of America, United kingdom, Empire of Japan, Thiarian High Republic, Republic of Koko.
French Republic, Kingdom of Italy partecipated but did not signed.

Ships to be demilitarized or scrapped:
[spoiler=]United States of America:
BB-32 Wyoming to be scrapped or converted to training duties.

United kingdom:
BC Tiger to be scrapped.
BB Iron duke to be demilitarized

Empire of Japan:
BB Settsu to be scrapped.
BC Hiei to be demilitarized and converted to training duties.

After the Signin of the Toumachi Treaty in 1897 a basic draft for new naval construction was quickly developed and approved by the Naval Staff. The plan called for the construction of two protected and two armoured cruisers, which in turn necessitated a few destroyers for escort duties.
To fulfill this requirement the Naval Staff ultimately choose to build 9 Destroyers based on the Murakumo Class design recently ordered by the IJN. The original plan called for them to be built locally, but by early 1901, when the last of the 4 Cruisers had been laid down it became clear that the newly built Toumachi Naval Arsenal was not able to handle all that work at once, more so since even the first Cruiser, laid down in 1897 had yet to be launched.
Those issues led to the eventual commitment for three destroyers to be built at the John I. Thornycroft & Company Yard and another three at the Yarrow Shipbuilders, Great Britain.
The first unit, Kuchikukan-1, Was laid down at Yarrow in 1901, launched in 1902 and commissioned during the same year.
Ultimately three ships were eventually built in Koko yards, Kuchikukan-4, Kuchikukan-7 and Kuchikukan-9. One last time modification before construction started was to shift to a modified Shirakumo Class design, which in turn was a modified Murakumo ordered by the IJN.The last ship was in service by 1905.
The Kuchikukan 1 Class had each ship named after it's pennant, and no unit ever recieved a name during their career. They were 68,6m long -1,1m more than a standard Shirakumo in the vain attempt to mitigate the wetness of the bridge at high speed with a longer turtleback forecastle-, 6,3m abeam and had a draft of 1,8m. They displaced 337tons standard and were capable of a 30knot top speed. armament was made up by two QF 12pounders and four 57mm guns, all in single mounts, the former placed above the bridge and at the stern, the latter mounted amidship, on sides. Two single 450mm torpedo tubes completed the armament.
While in commission 8 of the Destroyers usually made up two DesRons of 4 ships each, with the 9th unit usually retained in reserve, for training duties and to replace any of her sisters in case drydocking was needed. As the Armoured and Protected cruisers they were supposed to escort were completed too late to take part in the Russo-Japanese war, their career was quite uneventful, except for some patrol duties during the closing days of WWI.
As the fleeet was expanding and newer, larger, types of Destroyers were beign commissioned Kuchikukan 1 Class began to leave the fleet starting with the lead ship in 1921. Then the Washington Naval Treaty acclerated things even furter: with the immediate decommissioning of the oldest Protected and Armoured Cruisers Koko's Navy found itself with a surplus of Destroyers. While a large number of Light Cruisers were expected to enter service within the next four years it was also true that at least a dozen newer destroyers were filling, or were about to fill, the shipyards. Simply keeping the Kuchikukan 1 Class in service when they were not yet needed only to be replaced by new constructions as soon as the Light Cruisers would have joined the fleet was deemed not worthy of the expense. All eight remaining units were decommissioned at once in 1922, and only a last-time decision by the Naval Staff to convert them into minelayers saved them to join the lead ship in the scrapyards.

*A special thanks to Eswube and Acelanceloet for the Generic Ship Guide guide they made sometime ago, looking at it before drawing this DD was quite helpful as my knowledge of pre WWI ships is literaly zero.

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Ordered just as the new century started the the Nintoku Class Armored Cruisers were the second step (after the Protected Cruisers) in the process of Koko's Navy expansion. The two ships were almost a carbon-copy of the Asama Class that had just entered service with the IJN, sharing almost all dimensions, armor and weapon features with their Japanese siblings. While the Asamas were built overseas at the Armstrong Withword shipyards, United Kingdom, Nintoku, and her sister Jimmu were ultimately committed to Toumachi Naval Arsenal and laid down in 1900 and 1901 respectively. Construction lasted around five years for each ship, with the last beign commissioned in 1906.
The main difference between the Asamas and the Nintokus was impossible to be noticed unless the ships were drydocked: Nintoku once built measured 133,2m overall, comapred to the 134,7m of the Asama. This because Koko's Armored Cruisers lacked the protruding ram bow the Japanese ships had. Another difference were the omitted 12pounder gun positions at the bow as they were deemed too wet, the number of 2.5pounder rapid fire guns was also cut form 7 to 6.
Overall, Nintoku and Jimmu were armed with 4 203mm guns in two twin turret, 14 152mm ones in single casemate mounts, 10 76mm 12ponders and 6 47mm 2.5 punder guns. Four torpedo tubes were placed below the waterline, 2 on each sides. The fifth at the bow featured on the Asamas was dropped. The Nintoku class displaced 9.526T standard, some 300 less than the Asama class, still, top speed was inferior, at 20,8knots instead of 21.5, this mainly as a result of construction issues withing Toumachi Naval Arsenal, as delays and problems emerged during boiler developement and production, straining the still low experienced designers, engineers and manpower of Koko shipyards.
Nintoku was officially commissioned in October 1905, already too late to take part in the Russo-Japanese war, then her post-shakedown trials were plagued with multilpe engine and weapon issues, and dragged for so long that devoider her of the chance to act as Koko's flagship.
Jimmu was commissioned by mid 1906, and enjoyed a luckier career than her sister. Having learned from Nintoku's trials, all issues that emerged during Jimmu's post-shakedown trials were quickly resolved and she joined the Fleet as Koko no Kaigun flagship shortly after, mantaining that role until december 1907.
Meanwhile, the rapid developement of naval Armaments and concepts had already gone past ahead of the two Nintokus, and ultimately HMS Dreadnought commissioning in December 1906 virually made all earlier naval constructions obsolete. Despite this, Nintoku and Jimmu would have remained the most advanced units at Koko's disposal for another six years.
Nintoku finally took on flagship roles in December 1908, serving as such until December 1910, she was then Drydocked for maintenance and replaced by Jimmu until March 1912, when the first of the two Goryo Class Battlecruisers entered service.
During WWI Nintoku and Jimmu were left in home waters and did not took part in any major event, just Jimmu briefly sortied in October 1914 to provide distant screening to the Imperial Japanese Navy while it seized German colonies in the Pacific.
After the war the two ships were deemed obsolete and reclassified as reserve units, as new Light Cruisers started to join the fleet by 1920 the Nintokus were relegated to training duties, then abruptly decommissioned after the signing of the Washington Naval Treaty and immediately scrapped.

Ships in class: (laid down-launched-commissioned - fate)

Nintoku 1900-1903-1905 - Decom 1922
Jimmu 1901-1904-1906 - Decom 1922

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Sources and documentations are the most welcome.